More than 12 miles of Louisiana coast have been closed to fishing after tar balls and other toxins are discovered.

A Louisiana Wildlife and Fisheries officer walks along an oiled beach at South Pass in southern Louisiana in 2011. (Photo: John Moore/AFP Global Edition)

The beaches of Elmer's Island in Louisiana are "littered with tar balls of every size," according to Robert Barham, secretary of the Louisiana Department of Wildlife and Fisheries. The oil and tar balls, probably originating from the BP Deepwater Horizon oil spill of 2010, were stirred up by Hurricane Isaac last week and extend as far as a mile out to sea, forcing the state to close 12 miles of Gulf coastline to fishing and other activities, the New Orleans Times-Picayune reported.

Barham told the press that the tar balls will be analyzed to see if they originated from the Deepwater Horizon spill.

A spokesperson for the U.S. Department of the Interior told Our Amazing Planet last week that an estimated 1 million gallons of oil from the Deepwater Horizon spill are hiding in the underwater sediment off the coast of Louisiana, as well as in marshes and on nearby beaches. The hurricane was expected to stir up sediment and release oil, pesticides, fertilizers and other toxic chemicals.

BP itself quickly released a press statement saying it was "premature" to say if the oil stirred up by Isaac was from Deepwater Horizon or any other source. "As state officials have made clear, it is important to fingerprint the residual oil to determine its origin." But BP said it "stands ready" to clean up the oil if it is connected to the Deepwater spill. Other tests in Florida, Alabama and Mississippi conducted on Sept. 1 did not indicate that oil found in those regions originated from Deepwater Horizon.

Oil wasn't the only thing that washed up this weekend: More than 15,000 dead nutria rats were found dead on Mississippi beaches following last week's hurricane. They were probably killed by the storm's water surges.

Garret Graves, who advises Louisiana Gov. Bobby Jindal on coastal issues, told Fox News that the beaches where the tar balls and tar mats were found "experienced heavy oiling during the oil spill." He called the new oil "a smoking gun" pointing to the Deepwater Horizon spill.

In related news, the U.S. Justice Department filed court papers on Sept. 4 calling out BP PLC for "gross negligence and willful misconduct" related to the Deepwater Horizon spill. The case is scheduled to go to trial in January 2013. If BP is found guilty, it could quadruple the civil damages the company would owe under the Clean Water Act, according to Reuters. BP released a statement denying that it was negligent. Transocean, the company that owned the Deepwater Horizon platform, did not release a comment.

The Deepwater Horizon spill was the largest oil disaster in U.S. history, releasing an estimated 4.9 million barrels of oil into the Gulf of Mexico over the course of 87 days beginning on April 20, 2010.